PowerPoint 2011 for Mac provides users with the option to disable the tracking of recently opened documents. If you do not wish PowerPoint to maintain the history of recent presentations then you can turn off this feature using the General Options.
Step 1: Launch PowerPoint 2011 and click PowerPoint menu then select Preferences from menu list.
Step 2: Click the General tab in PowerPoint Preferences screen.
Step 3: Navigate to General Option and un mark the checkbox with caption as ” Track recently opened documents “
Step 4: Click OK button to confirm and save the changes.